Most types of hobby or artists paints should work (e.g.acrylics or enamels)

Main problem will be that the material is rather porous, so it soaks up paint, unless you prime it really well.

Greetings
Dragoman

Hi. If I have an item printed in multicolor sandstone and I wanted to give a clear varnish to make it shiny, I should use a transparent primer, but I would not risk ruining the object's colors?
Thank you.